Subjects with impaired glucose tolerance (IGT) are at particularly high risk for diabetes; over time 50% or more will develop overt diabetes. Ginseng root is one of the most commonly used natural remedies in the United States and has been purported to improve glucose tolerance and prevent diabetes. Ginsenoside Re, a major constituent, has been implicated in the anti-diabetic effects of ginseng. The already widespread use of ginseng by the general population makes it a potentially appealing agent for the prevention and/or treatment of type 2 diabetes, if safety and efficacy could be demonstrated in carefully controlled clinical studies. The present proposal details plans to study the metabolic effects of ginseng and ginsenoside Re in subjects with impaired glucose tolerance. The specific aims are: 1. To determine the effect of ginseng extract and ginsenoside Re on: a) glucose tolerance, b) basal glucose production, glucose disposal and lipolytic rate, and c) insulin action in adipose tissue, liver, and skeletal muscle. The hypothesis will be tested that ginseng extract and ginsenoside Re will improve glucose tolerance in subjects with IGT by decreasing basal glucose production and lipolytic rates and enhancing insulin-mediated suppression of glucose Ra and glycerol Ra, and stimulation of glucose Rd. 2. To determine the effect of ginseng extract and ginsenoside Re on pancreatic beta-cell function. The hypothesis will be tested that ginseng extract and ginsenoside Re will improve pancreatic beta cell sensitivity to glucose in subjects with IGT. 3. To determine the effect of ginseng extract and ginsenoside RE on skeletal muscle insulin signaling. The results from this study could lead to the development of a new and important approach to the prevention and/or treatment of type 2 diabetes, if the hypotheses posed above prove to be correct and if ginseng and/or ginsenoside Re are well tolerated.